Electrical protective system



Sept. 8, 1936. pl FERR|S ET ALy 2,053,988

ELECTRICAL PROTECTIVE SYSTEM Filed Dec. 27, 1955 7199 V mommy UNITED STATES PATENT OFFICE ELECTRICAL PROTECTIVE SYSTEM of New York Application December 27, 1935, Serial No. 56,394

4 Claims.

This invention relates to electrical protective systems. This invention also relates to arrangements for simultaneously grounding a plurality of conductors when any one or more of the various conductors becomes impressed with a high voltage induced therein from a power circuit or other extraneous source. This invention further relates to apparatus for substantially reducing acoustic shock in the telephone receivers and other devices connected to the various exposed conductors when high voltages become impressed thereon.

A group of protector blocks, each having an air gap which breaks down at a predetermined potential, have recently been used in the telephone art for the protection of a group of conductors which are exposed to extraneous voltage elects. In these arrangements a resistor or saturating reactor is usually connected between the various protector blocks and ground. When the gap of one or more of the protector blocks breaks down upon the application of a high voltage to the exposed conductors, a substantial current will flow through the resistor or reactor. The resistor or reactor, as the case may be, is connected to apparatus including a relay which operates when current flows through the resistor or reactor. The operation of the relay may be employed to provide a plurality of circuits each of which will shunt one of the various protector blocks associated with one of the exposed conductors, thereby preventing the permanent short circuiting of said protector blocks.

In the arrangements just referred to, the circuits which are provided by the relay for the purpose of shunting the various protector blocks are completed some time after the extraneous voltage or voltages have reached the various exposed conductors. In other words, the operation of the relays to short-circuit the protector blocks is not instantaneous. During this interval of delay the voltage upon one of the exposed conductors may be different from that upon the other (or another) exposed conductor, due to the lack of symmetrical operation of the protector blocks. There Will, therefore, be a metallic voltage between any pair of such conductors and this metallic voltage may be suicient to cause acoustic shock in telephone receivers or other devices connected to these conductors. This metallic voltage, moreover, may be so high as to shock linemen and others working with the circuits.

The present invention is intended to overcome the defects just referred to. The apparatus ernployed in carrying out the principles of this invention will, in effect, simultaneously ground all of the exposed conductors when a single one of these conductors becomes impressed with a high and predetermined voltage such as that due to lightning or as the result of exposure to a power circuit. Before the various exposed conductors become grounded, the voltages applied to the various conductors will be equalized, in which case there will be very little metallic voltage between these conductors, and the danger to the apparatus connected to the circuits and to the people Working with the circuits will be greatly diminished.

This invention will be better understood from the detailed description hereinafter following, when read in connection with the accompanying drawing. Figure 1 of this drawing shows one embodiment of this invention illustrating a plurality of protector blocks connected to exposed conductors, and the circuits include what will be termed a discharge balance coil, a saturating reactor and apparatus for simultaneously grounding all of the conductors soon after any one of these conductors has become exposed to a large inductive effect. Fig. 2 illustrates an improved form of arrangement `for carrying out the principles of this invention in which the invention is applied to a phantom group of circuits.

Referring to Fig. l of the drawing, the reference characters L1 and L2 represent two of a plurality of exposed conductors which will be used for transmitting telephonie currents or other currents used in the transmission of signals. These conductors are connected to a pair of protector blocks P1 and P2, as shown. The terminals of the protector blocks P1 and P2 are connected to the terminals of a pair of equal windings of a discharge balance coil W1 and W2, which have the same number of turns and which are mounted upon a common core of, for example, iron, so that they will have a large mutual inductance therebetween. 'I'he midpoint or terminal common to the windings W1 and W2 is connected to ground through a saturating reactor or transformer Wo. A resistor R may be connected in shunt With the reactor We.

The terminals of the saturating reactor Wo are connected to the input terminals of a full wave rectifier B which may be, for example, of the copper oxide type. The output terminals of the rectier B are connected to the terminals of the Winding of a relay N. The armature at the left of the relay N and its contact, provide a circuit for shunting the protector block P1, while the armature at the right of the relay N and its contact, provide a circuit for shunting the protector block P2.

Similar protective apparatus may be connected to the conductors L1 and L2 at other points along their length, as indicated in the drawing.

When voltage becomes impressed upon the conductors L1 and L2, of suliicient amplitude to break down the gap of one of the protector blocks, for example, P1, but of insuicient amplitude tobreak down the gap of the other protector block, i. e., P2, current will flow from the conductor L1, through the winding W1, through the saturating reactor Wo and the parallel resistor Ro, to ground. The voltage appearing across the terminals of the saturating reactor Wo will be rectified by the rectifier B and the rectied current will operate the relay N, the armatures of which will provide circuits for shunting both of the protector blocks P1 and P2. Before both of the protector blocks become shunted by the circuits provided by the armatures of the relay N, the discharge balance coil windings W1 and W2 introduce their eiiect against acoustic shock, this effect being transmitted to the protector blocks and to the conductors L1 and L2 to which they are connected.

Immediately after the protector block P1 breaks down and so connects the conductor L1 to ground through the discharge balance coil winding W1 and the parallel arrangement of reactor Wo and resistor Ro, a large voltage will be induced in the discharge balance coil winding W2 by virtue of the close coupling between windings W1 and W2. The Voltage induced in the winding W2 is of such a magnitude and in such a, direction that it will bring about the break-down of the gap of the protector block P2. When this occurs the conductor L2 will be connected to ground through the winding W2 and the parallel arrangement of reactor W and resistor R0. Both of the conductors L1 and L2 will then be simultaneously grounded, as already pointed out, and large currents will be able to iiow freely between these conductors and ground.

The windings W1 and W2 are so wound about their common core that voltages impressed upon the respective exposed conductors L1 and L2 will cause current to iiow through the windings W1 and W2 and establish uxes in the common core of iron which are in mutually opposite directions. After both of the protector blocks P1 and P2 have become broken down, or after the armatures of the relays N have provided circuits in shunt with the protector blocks P1 and P2, the ow of current through the windings of the discharge balance coil will produce mutually opposite iiuxes in the core and these will practically balance and neutralize each other. Under such conditions the resultant ilux in the core will be practically negligible.

Thus it will be seen that the discharge balance coil windings W1 and W2 are so arranged in the circuit that they tend to equalize the voltage to ground of the two exposed conductors L1 and L2, and they therefore prevent the appearance of a metallic voltage between these conductors of such a magnitude as to produce acoustic shock either in the operators receiver or in the subscribers receiver, or in any other apparatus connected to the circuit. The windings W1 and W2 produce their greatest eiect immediately after a single protector block has broken down, and they produce voltages which not alone swiftly break down the gap of the other protector block but they also speed up the operation of the relay N which is used for the purpose of shunting the various protector blocks out of the circuit. In other words, any asymmetrical operation of the pro-'- tector blocks is quickly overcome by the eiect of the windings W1 and W2, and the asymmetrical condition is readily converted into a symmetrical condition without the production of metallic voltages and the accompanying acoustic shocks.

Fig. 2 shows an improved arrangement which may be used in connection with a phantom group of circuits. Here the reference characters L3 and L4 represent one of the side circuits, the reference characters L5 and Le represent another of the side circuits, and these two side circuits, together, comprise a phantom circuit, as is well known. The conductors La and L4 are connected to the protector blocks P3 and P4, while the conductors L5 and L5 are connected to the protector blocks P5 and P6, respectively. The protector blocks Ps and P4 are connected to equal discharge balance coil windings W3 and W4, While the protector blocks P5 and P5 are connected to the discharge balance coil windings W5 and W5, respectively, the various discharge balance coil windings Wa to We being similar to those described in connection with Fig. 1. The conductor common to the windings W3 and W4 is connected to the conductor common to the windings W5 and W5 through a circuit which includes additional discharge balance coil windings W1 and Wa which are also equal windings upon a common core Such as iron. The terminal common to the windings W1 and Ws is connected to ground through a saturating reactor across which a resistor R0 may be connected, if so desired.

As in Fig. l, the reactor W0 is connected to the input terminals of the full wave rectier B, while the output terminals of the full wave rectifier B are connected with the windings of a pair of relays designated N1 and N2, as shown. A suficient voltage appearing across the reactor Wo will be rectiiied by the rectifier B, and the current derived from the rectifier will iiow through the series-connected windings of the relays N1 and N2 and cause their operation. The two armatures of the relay N1 will provide circuits for shunting the protector blocks P5 and P4, While the armatures of the relay N2 will simultaneously provide circuits for shunting the protector blocks P5 and P6.

It will be apparent that if one of the protector blocks P3, for example, breaks down because of the presence of a large extraneous voltage upon the conductor La, the voltage induced in the discharge balance coil winding W4 will promptly bring about the breakdown of the gap of the protector block P4. Similarly, the breakdown of the gap of either of the protector blocks P5 or P5 will produce an inductive elect in the discharge balance coil winding associated with the protector block that is not broken down so that that protector block may also be promptly broken down. By virtue of the common connection of the discharge balance coil windings W3, W4, W5 and Ws through the circuit which includes the discharge balance coil windings W1 and Wa, any breakdown of one of the circuits associated with any one of the various conductors as, for example, L4, will cause a voltage to be produced across the winding Ws, which will bring about the prompt breakdown of the gaps of both of the protector blocks P5 and Ps. Similarly, any breakdown of the gap of one of the protector blocks, such as P5, will not alone bring about the breakdown of the protector blocks P5, but a large voltage will be induced in the discharge balance coil winding W7 which will promptly break down the gaps of both of the protector blocks Pa and P4.

Thus, it will'be observed, the discharge balance coil windings W3 and W4 are provided to protect the side circuit of conductors La and L4 against acoustic shocks to the receivers or other devices connected with that side circuit, and the discharge balance coil windings W5 and Ws protect the side circuit composed of conductors L5 and Le against acoustic shocks to the receivers or other devices connected tothe latter side circuit, at the same time the discharge balance coil windings W1 and Ws act to diminish acoustic shock to any receivers or apparatus connected to the phantom circuit formed by the two side circuits.

It will be apparent that in Fig. 1, for instance, the resistor Ro, coil Wu, rectifier B and relay N may be replaced by an'alternating current `relay having a winding connected between the terminal common to windings W1 and W2 and ground and preferably wound upon a saturating core, the relay having two armatures which may be used to shunt the blocks P1 and P2 in the same manner as described in connection with relay N.

While this invention has been shown and described in certain particular arrangements merely for the purpose of illustration it will be understood that the general principles of this invention may be applied to other and widely varied organizations without departing from the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. Apparatus for the protection of a pair of conductors exposed to inductive or extraneous interference comprising a pair of protector blocks, a pairl of coils wound upon a common core of magnetic material, a saturating reactor one terminal of which is connected to ground and the other terminal of which is connected to both of the exposed conductors, the connection to each of the exposed conductors being established through one of the coils wound upon the iron core and the corresponding Vprotector block, and means coupled to the saturating reactor responsive to a voltage impressed thereacross for simultaneously shunting both of the protector blocks.

2. Apparatus for the protection of a pair of conductors exposed to inductive or extraneous interference and for preventing -acoustic shock in circuits connected to said conductors comprising a pair of protector blocks, a pair of coils wound upon a common core of magnetic material, each of which is connected to one of the exposed conductors through its corresponding protector block, a saturating reactor common to the coupled coils of wire, and means including a relay responsive to the ow of current through the saturating reactor providing paths in shunt with the protector blocks.

3. Apparatus for eliminating acoustic shock in the circuits of a pair of conductors exposed to inductive or extraneous interference comprising two gapped devices, two coils of wire between which there is a high mutual inductance, each of the exposed conductors being connected to ground through one of the gapped devices and one of the coils 'of wire, and means responsive to a breakdown of either of the gapped devices for producing circuits forx shunting both of said gapped devices. l

4. Apparatus for the prevention of acoustic shock in a plurality of conductors which form two side circuits and a phantom circuit and are exposed to inductive or extraneous interference comprising a plurality of protector blocks two of which are connected to each side circuit, three pairs of coils, the coilsof each pair being wound upon a common core so as to have a high mutual inductance therebetween, one pair of coils being connected respectively to one pair of protector blocks connected to one of the side circuits, the coils of another pair being connected to the protector blocks associated with another of the side circuits, means for connecting one of the coils of the third pair in common with the two coils of each of the other pairs associated with the side circuits, and means responsive to the breakdown of the gap of any one of the various protector blocks for providing circuits in shunt with all of the protector blocks.

LIVINGSTON P. FERRIS. RICHARD KARL HONAMAN. LEONARD S. INSKIP. 

